Electroresponsive device



B.'R. TEARE, JR.,l E1' AL 2,014,869 ELECTRORESPONSIE DEVICE Sept. 17,1935..

Original Filed Nov. '15, 1932 CURRENT CURRENT CURRE N 7' Max A Whi'cngibymm m Their' Attorney Parente/a sept. 17, 1935 yUNITED STATES PATENTOFFICE Application November 15, 1932, serial No. 642,736

Renewed May 25, 1935 19 Claims. (Cl. 175-294) Our invention relates toelectroresponsive devices and particularly to such devices which areadapted to be used in electrical regulators and regulating systems.

An example of a practical application of our invention is to the controlof the electrical system of automobiles. In order better to understandthis application it will be helpful first to vdiscuss briey theelectrical system of automobiles, with particular emphasis on theshortcomings of the usual system and a brief description of thecharacteristics of an ideal system.

Automobile electrical systemsl usually include an electrical generator,driven by the engine,

l5 a storage battery, and various load devices, such as `the ignitionsystem, lights, starter motor, horn, etc. The storage battery isprovided for operating the various load devices when the engine is notrunning. Consequently, it is highly desirable that this battery bemaintained in good condition, and as nearly fully chargedas possible, atall times. The battery is charged by the generator when the engine isrunning and as the engine speed varies within Wide limits it isnecessary to provide some. sort of regulating means to control thecharging rate. -The regulating means which has been generally adopted isa special design generator, known as the third brush generator. Such agenerator, when operated at any one speed, has inherently asubstantially constant-current characteristic, the values of current towhich it regulates being differentat different speeds but substantiallyunaffected by the resistance or by the counter-voltage of the load.

With such a system the charging rate tends to be constant at any givenspeed irrespective of the need of the battery. Such a chargingcharacteristic has the following disadvantages. It is necessarily acompromise, or average, rate and therefore is too high when the batteryis fully charged while it is too low to bring the battery quickly up tofull charge if it is severely discharged. Furthermore, in Isuch a systemthe voltage will vary widely with changes in circuit v resistance. Thus,if there is a loose battery terminal the voltage will go up, in aneffort to maintain constant current, and this high voltage will reducegreatly the life of the light bulbs. This 5o effect is also produced, toa lesser extent, by

changes in the battery voltage, as this is equivalent to a resistancechange in the circuit.

An ideal system would be one in which the generator voltage wasconstant, at a value which 55 would just maintain the battery fullycharged after it became fully charged. With such a system a fullycharged battery could not be injured by prolonged driving. Also, thecharging rate, or current,y would increase in proportion to the state ofdischarge of the battery because as the battery became discharged itscounter voltage would decrease' and consequently a greater net voltagewould be available for circulating 4the charging, current. A greatlydischarged battery would therefore be quickly brought up to full mcharge. Also, as the voltage was constant, the life of the light bulbswould be prolonged.

An ideal system should also have the charging circuit so arranged thatfor any given state of charge of the battery the charging current should15 be as high as the battery could stand. This is because such anarrangement would most quickly bring a discharged battery up to fullcharge. Such a rate is one which is just below the rate which producesgassing, because it is the gassingk which is injurious to a battery. Ithas been found that vthe maximum non-gassing current of a lead storagebattery, for any state of charge, is substantially directly proportionalto the percentage by which it lacks full charge.

It is not particularly diicult to provide a. voltage regulator whichwill maintain constant voltage but, for certain practical reasons, asimple, or ideal, constant voltage system is not always feasible. Onereason is' that in order to supply the maximum non-gassing chargingcurrent to a greatly discharged battery it is necessary to provide anexcessively large generator. If a smaller generator isemployed it willbe necessaryto provide means for preventing its being loverloaded whilepermitting it to supply charging current at the maximum non-gassing ratewithin its capacity.

In accordance with one feature of our invention we provide novel meansfor accomplishing 40 this result. v

Another reason that the simple constant voltage system is not alwaysfeasible is that the spread between the constant generator voltageandthe battery voltage will preferably be quite 45 small. As the voltageof the generator drops to zero when it is at rest, all automobilesystems are provided with a reverse current relay, or cutout, forpreventing discharge of the battery at such times. The cutouts have awinding, responsive to the voltage of the generator, for closing thecharging circuit when the generator voltage exceeds the battery voltage.With a simple constant voltage system the spread between these voltageswill often be insufficient to give reliable and positive cutout action.

In accordance with another feature of our invention we provide novelmeans for securing positive and reliable cutout operation in a constantvoltage system.

The embodiments of our invention which we have illustrated and describedare in the form of special electromagnetic structures and while thesestructures may be used either singly, or in combinationto produce anovel electrical regulator with improved and special characteristicsadapting it to a constant voltage automobile battery charging system, wewish to point out that our invention is not so limited and that thesestructures may have other uses, such as in relays and electricalinstruments, for example.

An object of our invention is to provide a novel electroresponsivedevice.

`Another object of our invention is to so contrive an electromagnetstructure, having a single pair of main, or working, pole faces and aplurality of exciting windings, that the variations of current in acertain winding, or windings, will cause substantially no change in themain airgap flux between certain limiting values of this current butwill cause substantially large changes in main air-gap flux at values ofcurrent outside of those limits, or between certain other limits.

A further object of our invention is to provide in an electromagnetstructure, having a single pair of main poles, a voltage winding and oneor more current windings, aA characteristic in which the flux across themain air-gap is determined solely by the voltage throughout a certainrange of current variation lbut is determined jointly by voltage andcurrent throughout certain other ranges of current.

A still further object of our invention is to g provide a novelgenerator voltage regulator which holds a substantially linear relationbetween generator voltage and generator current, between certain limitsof said current and which causes relatively abrupt changes in saidrelation at current values outside said limits.

Our invention will be better understood from the following description,taken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the drawing, in which similar reference characters denote similarelements throughout the several figures, Fig. 1 shows the combination oftwo windings and a magnet structure in which the flux across the mainair-gap is determined solely by the current in the rst winding so longas the current in the second winding is less than a certain substantialvalue but is determined jointly by the currents in both windings when'rthe current in the second winding is greater than that value.

Fig. 2 shows the nature of the regulating characteristic provided when astructure inv accordance with Fig. 1 is used as a vibrating-contactvoltage regulator for a generator.

Fig. 3 shows a different'arrangement of magnet structure and twowindings whose specific purpose is different from that of Fig, 1. InFig. 3 the rise of current in the second winding from zero to arelatively small value causesa substantial change of flux across themain air-gap but further increases of that current cause substantiallyno further changes in main air-gap flux.

Fig. 4 shows the nature of the regulating characteristic provided when astructure in accordance with Fig. 3 is usedas a vibrating-contactvoltage regulator for a generator.

Fig. 5 shows a battery-charging generator system controlled by avibrating-contact voltage regulator in which are included the featuresof Fig. 1 and Fig. 3.

Fig. 6 shows the regulating characteristic of the arrangement; of Fig.5.

Referring now more particularly to Fig. l: A side view is shown of anelectromagnet of the horseshoe type having a main core I which issubstantially U-shaped and which is provided with a magnetizing winding2, preferably of the shunt tym. A magnet amature 3, mounted on a spring4, or other equivalent support, is controlled by the flux across mainair-gaps 5 and 6 (principally by the flux across 6) so that when theflux exceeds a certain value armature 3 will operate a circuitcontroller, such as opening a set of contacts 1, for example. As shown,spring 4 is attached, at its upper end, to a fixed support. Mainain-gaps 5 and 8 are preferably of equal reluctance.

Associated with main core I is a magnetic shunt member 8, which isillustrated as being U-shaped. A magnetizing winding 9, which ispreferably of the series type, is provided for member B. The magneticcircuit of U-shaped shunt member 8 is completed through a portion ofmain core I. Reluctance, preferably in the form of air-gaps, isintroduced into the path of the ux excited by winding-9. For thispurpose, any number of airgaps may be used, outside of member I butvariously arranged as preferred. As examples, one

air-gap may be used, located at I8 or at Il, or air-gaps at both I andII, as shown. Also airgaps may be interposed transversely within member8, if desired. The total reluctance of these air-gaps I0, II or the likeis preferably much less than that of the sum of main air-gaps and i.'I'he total length and surface of member 8 should preferably be notunnecessarily great and the cross-section of 8 should preferably beequal to, or somewhat `greater than, that of the main bodyof I`.

Magnet core I has a portion thereof which is preferably more readilymagnetically saturable than the remainder, such as a restricted sectionI2 of short length. We have found that a restricted section of about onequarter of an inch in length gives satisfactory results in a structurein which the legs of core I are about one and a half inches long. Thisrestricted section is located between the faces of air-gaps I8 and II.Restricted crosssection I2 should preferably be saturated by not morethan approximately onehalf of the flux which would be required to saturate 8, or the unrestricted cross-section of I. Specifically, ifelements I, 8 and I2 are of like material the, restricted crosssectionI2 should preferably be not more than approximately onehalf that of I or8. For best results it is important that there be no appreciable air-gapreluctance between restricted section I2 andthe remainder of magnet coreI. To this endl restricted section I2 should be of one piece with theremainder of I.

Armature 3, if. preferred, may be of much less cross-section than I.

The magnetic material may be ordinary coldrolled steel, or the like, andshould preferably be given a thorough magnetic anneal. If preferred, ahigher grade material such as magnetically annealed ingot iron, orsilicon steel, may be used.

The various proportions, including the airgaps andthe strength of shunttype winding 2 are so chosen that with a normal exciting current inwinding 2, but no current in winding 9, the magnetic flux densities aresubstantially below saturation, even in restricted section I2 andarmature 3, and are far below saturation in 8 and the unrestrictedsections of I.

For reasons appearing hereinafter it may be preferable in someembodiments to use a Winding I3 connected electrically in series withwinding 9, although in other embodiments winding I3 may be of noadvantage. When used, winding I3 is placed about magnet core I and soconnected that when energized by current in the normal direction windingI3 opposes winding 2.

'I'he operation of the magnetic circuits of Fig. 1 will now be describedin a general way, deferring until later the explanation of the effect ofwinding I3 and of certain leakage effects and certain effects of ironreluctance. In order to facilitate an understanding of the operation ofthe specific illustrated embodiments of our invention, from the drawing,the normal polarity of the various windings in Figs. 1, 3 and 5 has beenindicated.

Assume that the current in winding 9 is zero and assume normal currentis passed through winding 2, which is connected to excite a ilux in coreI in a counterclockwise direction. Since restricted section I2 isunsaturated under this condition, and is of short length, its reluctanceis substantially zero with respect to that of air-gaps I plus II inseries. Hence most of the flux excited by winding 2 passes through I2rather than through 8.

Let winding 9 be so arranged that when energized by current in a normaldirection it excites a component of ux-whose direction through 8 is fromleft to right and whose direction through I2 is from right to left. Thiscomponent of iiux thus traverses an auxiliary magneticy circuitcomprising elements 8 and I2. Now assume that the current in winding 2remains unchanged but that the current in Winding 9 is increased fromzero to a moderate value. The air-gaps I0 and II restrict to a moderatevalue the flux excited bythe winding 9. Under this condition restrictedsection I2 forms avery low-reluctance path whereas main air-gaps and 6are of relatively high reluctance. Hence practically all of theuxexcited by 9 is short circuited by I2 and practically none of thisiiux escapes to cross main air-gaps 5 and 6. Therefore the magnetic pullon armature 3 is substantially no diierent than at zero current in, 9.

Now assume that ,the current in 9 is increased beyond this moderatevalue. As the flux excited by the current in 9 increases further, acondition is reached at which the iron of restricted section I2 beginsto saturate. Thereupon the reluctance of section I2, heretoforenegligible, increases rather suddenly to a'. value which, although stillmuch less, is ofv substantial magnitude compared with the reluctance ofmain air-gaps 5 and 6. Accordingly, a substantial fraction of the uxexcited by winding 9 crosses air-gap 6, thence passing along thelengthof armature 3 to cross air-gap 5, whence it returns through theupper and left-hand sides of I. Thus, the energlzation of shunt Winding2 remainingconstant, the magnetic pull across air-gap 6 begins toincrease rather rapidly after the attainment of the above-mentionedcurrent in winding 9 at which restricted section I2 begins to besaturated. At still further increase of current in winding 9 restrictedsection I2 becomes highly saturated and its reluctance becomesprogressively much greater. 'Ihe entire component of flux excited bywinding 9 has now further increased and because of the progressivelyincreased reluctance 5 of I2 a progressively greater proportion of thiscomponent of flux crosses the main air-gaps 5 and 6, thereby increasingthe air-gap pull at an augmented rate.

The action has been described on the basis 10 that the current inwinding 2 remains constant, so that increases of current in Winding 9beyond the value at which section I2 begins to be saturated causeincreases of flux across main air-gaps 5 and 6. Consider now the actionwhen l5 the structure of Fig. 1 is used in a generator voltage regulatorof the vibrating-contact type. Such a regulator is shown in completedetail in Fig.'5,

in which windings 2 and 9 are responsive, respectively, to the voltageand current of a regulated generator. In such a voltage regulator theaction is, fundamentally, that the regulator operation tends to maintainconstant ux at its own main air-gap. 'Ihat is to say, the regulator sooperates. as to maintain a dynamic, or vibrating, equilibrium betweenthe force of spring I and the magnetic pull at air-gaps 5 and 6. Whenthe current in winding 9 increases to a value `at which restrictedsection I2 begins to saturate and when therefore a fraction of the iiuxexcited by current 9 crosses the main air-gaps 5 and 6, as describedhereinbefore, the condition of equilibrium between main air-gap pull andspring force is satis-J ed by a smaller-,value of that component of tluxwhich is excited by shunt winding 2. Hence the regulator now regulatesat a lower voltage impressed upon winding 2. The nature of thecharacteristic of voltage versus current resulting therefrom isrepresented in Fig. 2 in which dotted line b c d' is typical of resultsprovided by cer- 40 tain embodiments, and solid line b c d is typical ofother embodiments.

In the foregoing general description of the operation of Fig. 1 wedeferred the explanation of certain leakage and iron reluctance effects,which we now proceed to explain. At low and moderate currents in winding9 and accordingly at low and moderate flux densities in restrictedsection I2, the reluctance of I2, although quite low, is not absolutelynegligible compared with the reluctance'of the main magnetic circuitthrough airgaps 5 and 6. For this reason a small component of the Iluxexcited by winding 9 traverses main air-gaps 5 and 6 even'at currentsless than saturating values of restricted section I2. Hence theregulation curve, unless otherwise compensated, may droop somewhat asshown by line b c d in Fig. 2. If this droop is'greater than desired itmay be corrected by the use of a differential series winding I3 whosearrangement has ci) been described. As the current increases, Winding I3offers an increasing opposition to winding 2 hence increases the voltagerequired across winding 2 for the maintenance of vibrating equilibriumof the regulator. Hence, by the use of winding I3 the droop incharacteristic b c d' can be compensated and a characteristic such as bc d can be actually obtained.

In some embodiments we have obtained a characteristic substantially likethat of b c d without the use of differential series turns on member I.It will be observed that in Fig. 1 spring 4 carrying armature 3 issupported at the top, farthest from air-gaps II and 6 and member 8.Furthermore, the radius from the spring support,

3, spring 4 and its support are upside down from the showing of Fig. 1so that the air-gap 4, which is near air-gap II and core 8, is eiectiveat only a short radius and air-gap 5, which is remote from gap II andcore l, is eective at a long radius. With this latter arrangement in avibrating regulator we have found that the voltage regulation issubstantially drooping even at moderate currents, the characteristicresembling curve b c' d in Fig. 2 but with steeper droop throughout. Ittherefore tends to be important whether the center about which armature3 oscillates is nearer gap 5 or is nearer gaps 4 and II. We believe thisdifference of characteristic is caused as follows: Refer to Fig. 1 inwhich the pivot of amature 3 is near gap 5 but remote from gaps 5 and II. Let the current in winding 9 increase to a moderate value at whichthe flux excited by winding 9 is substantial but less than thesaturating value of restricted section I2. The reluctance of air-gap I Iis substantial hence some flux fringes outward proceeding from theright-hand end of member l to enter armature 3 at its rear surface,sides and bottom edge. 'This leakage flux, because of the directions atwhich it enters armature 4 does not add to the pull upon l. Afterentering armature 3 from member l ythis leakage iiux divides into twocomponents, approximately one-half of which traverses armature l andcrosses air-gap 5 additively to the main flux. The other half of theflux leaking from 8 to 1 traverses air-gap 6 against the direction ofthe main flux. Thus the leakage flux described increases the effectiveflux, hence the pull, across gap 5 and decreases the effective iiux,hence the pull, across gap 5 by an equal amount. Since the lever arm ofvgap 5 is much greater than that of gap 5 ythe net torque upon armature3 tending to open contacts 1 is decreased by the action of the leakageflux described. In a vibrating regulator this requires an increase ofcurrent in winding 2 to provde vibrating equilibrium against the effectof the leakage ilux just described. It has been explained hereinbeforethat the reluctance of restricted section I2 when unsaturated causes aslight droop such as b c' in Fig. 2. By proper proportioning, theleakage effect just described can be made to compensate the droop b c'lso as to give substantially uniform voltage regulation between b and c.To increase the compensating eiiect by the leakage flux describedair-gap I I may be increased in length and gap I4 correspondinglydecreased in length. Conversely to decrease this compensating edectair-gap II may be decreased in length and sir-gap Il may be increased inlength. Alternatively. or additionally, this compensation may beadjusted by positioning member l nearer to or farther from armature 4.

Conversely, if in Fig. 1 all else is unchanged but the assembly ofcontacts 1 and amature I and spring 4 with its support is inverted fromthat shown, the flux across gap 5, which is increased by the leakage asdescribed. acts at the maximum lever arm and the flux across gap 4,which is correspondingly decreased, acts at the minimum' lever arm.Hence this leakage flux in this arrangementaccentuatesthe droop.

Still another leakage phenomenon is as follows: When restricted sectionI2 approaches saturation and its reluctance accordingly becomessubstantial a ysubstantial leakage flux occurs directly in parallel withrestricted section I2. This increases the ampere-turns in winding 5required for each degree of saturation of section I2. Hence, if the'performance of a specific design is calculated without allowance forthis leakage directly in parallel with restricted section I2, and ifcurve b c d of Fig. 2 is taken to represent the performance on the basisof the simplified calculation, the actual curve will be found to have aless steep droop from c to d, points beyond c toward d occurring athigher currents than calculated. The effect predicted by the simplifiedcalculation can be substantially eliminated in practice by increasingthe sum of the air-gap lengths of III and i I, increasing also thenumber of turns of winding 9 over those of the simplified calculation,and iurthermore, making sure that member 4 is oi sufficientcross-section to keep it substantially unsaturated.

If the slope of the drooping part of the characteristic c/dis'substantially as desired but it is desired that point c, at which thedroop begins, shall occur at a higher current, winding 9 may remainunchanged and the sum of air-gaps III and II may be increased.Conversely point c may be made to occur at lower current by decreasingair gaps I and II.

The performance may be affected, in some cases adversely, by thepresence of other magnets, or of other iron bodies, very near the magnetstructure of Fig. 1.

Turning now to Fig. 3, we show therein a side view of a magnet whichdiffers from the magnet of Fig. 1 in that it is provided with extensionsI4 and Il between which there is a magnetic member I5. Reluctance isinserted between member I and members I4 and I5, preferably in the formof air-gaps I1 and I4, although but one air-gap may be used if desired.The reluctance of gaps I1 and Il is preferably small with respect to thereluctanceof main air-gaps 5 and 6. Members I4, I5 and I4, and air-gapsI1 and I5, form a magnetic shunt, or by-pass, about a portion I9 of themain magnet core. Member I9 is surrounded by a winding 24, which may bea series winding.

amber I 5 is rendered readily saturable in any suitable way, such as bya restricted section 2l. We have found that a length of section 2| notgreater than about one-fourth of an inch, gives good results. Winding 2lhas a relatively large number of turns so that a relatively smallcurrent will cause enough flux to circulate via Il, Il, Il, I5, I1 andI4, to saturate restricted section 2i thoroughly. Restrictedcross-section 2| should preferably be saturated by not more thanapproximately one-quarter of the flux which would be required tosaturate elements I4, I5 and I6 and the unrestricted cross-section ofI5. Specifically if elements I4, Il, I5, Il and 2| are of like materialthe restricted cross-section 2l should preferably be not more thanapproximately one-quarter that of I4, Il, II and Il.

'Ihe magnetic material should preferably be given a thorough magneticanneal and may be of any oi' the grades mentioned in describing Fig. 1.

Armature l, contacts 1 and spring 4 correspond to like parts in Fig. 1.

Winding I3 is preferably used in Fig. 2, ranged in the manner describedunder Fig. 1.

Neglecting, for the moment, the benefit derived from winding I3, whichis explained hereinafter, the operation of the magnetic circuits of Fig.3 is as follows: Assume zero current in series winding 28 and assumethat normal current traverses shunt Winding 2, which winding isconnected to cause a flux in the counter-clockwise direction, i. e. tothe left through I4, down through I 8, and

to the right through I6. Since the restricted section 2| is unsaturatedand is of short length its reluctance is substantially zero comparedwith that of air-gaps I1 and I8. Hence substantially all of the fluxexcited by shunt winding 2 passes through 2| rather than acrossair-gapsI1 and I8.

Let winding 20 be so connected that when energized by current in anormal direction a flux is excited thereby whose direction through I9 isdownward i. e. is cumulative therein with the ux excited by winding 2.Now let the current in winding 28 be increased from, zero to arelatively small value, the current in winding 2 being assumedunchanged. A relatively large component of flux will be excited in I9 bywinding 20. The

greater fraction of the flux so excited passes through the relativelyshort air-gaps I1 and I8 but another fraction crosses air-gaps and I5vcumulatively with the main flux excited by winding 2. The pull onarmature A is substantially increased thereby over that caused by theshunt excitation alone.

Now let the current in undergo a further small increase. Restrictedsection 2| becomes partially saturated so that the further increase ofilux excited by 20 is small, hence the ux crossing main air-gaps 5 and 6undergoes only a slight further increase. A further increase of currentin winding 20 causes restricted section 2| to become completelysaturated so that substantially no further increase of flux is excitedby winding 28 and consequently no further increase of ux occurs acrossair-gaps 5 and 6.

The action of Fig. 3 has been described on the basis that the current inwinding 2 remains constant. Consider now the case in which the struciture of Fig. 3 is used in a generator voltage regulator of thevibrating-contact type wherein windings 2 and 20 are energized inaccordance with the voltage and current, respectively, of a generator,as in Fig. 5. As mentioned in explaining Fig. 1, such a regulator tendsto maintain constant flux atits main air-gap. During the rise of currentin winding 20 from zero to the relatively small value at whichsaturation occurs, the fraction of the flux excited by 20, andtraversing main air-gaps 5 and Ii as described, aids in overcoming theforce of spring 4` so that a reduced component of flux excited bywinding 2 is suiilcient for maintaining equilibrium.' Hence theregulator now regulatesat a lower voltage impressed upon winding 2 thanit did at (zero cur-.

rent in 20. Since restricted section 2| becomes completely saturated ata relatively small current in winding 20 further increases of current in20 have very little further eiect upon the main airgap ux and theregulated voltage remains nearly constant at further increases ofcurrent in winding 28. f.

The nature of the characteristic of voltage versus current resultingfrom the above action is represented in Fig. 4. Point b represents thecurrent at which restricted section 2| becomes substantially saturated.Even whenithe iron of restricted section 2| becomes saturated, furtherincrements of current in Winding 20 will cause slight increments of fluxthrough 2|. Hence if winding I3, or some other compensating means, isnot present the characteristic will droop slightly beyond b asrepresented by dotted line b c. By the uspofdifferential series WindingI3 this droop can be compensated, as will be understood from theexplanation of the operation of Winding I3 in Fig. 1 hereinbefore. Hencea substantially uniform regulated voltage can be obtained at currentsgreater than b, as shown by b c in Fig. 4.

The constructions of Fig. 1 and Fig. 3 may be combined in a vibratingvoltage regulator to provide a characteristic having the initial droop,a b as in Fig. 4, thereupon a substantially at voltage regulation as b cin Figs. 2 and 4 and at high loads a droop, as c d in Fig. 2. Such acombination is shown in Fig. 5 in which are included also the generator,battery and other essentials of a battery-charging system.

Fig. 5 shows a generator 22 driven by any suitable source of power (notshown), typically a variable-speed prime mover,= such as an automobileengine. Generator 22 has a shunt eld winding 23 controlled by avibrating-contact 35 regulator 24 in accordance with our invention forthe purpose of charging a storage battery 25.

A conventional cutout 26 is shown which closes automatically when thegenerator voltage rises to a predetermined value which has been selected30 to be higher than the maximum battery voltage. This cutout isarranged in the conventional manner with a shunt winding 21 and a serieswinding 28, the function of the series Winding being to open the cutoutwhenever the generator 3.5

voltage decreases sufficiently below that of the battery to cause asubstantial discharge current from the battery intothe generator.

A resistor 29 in series with-generator field 23 is short-circuitedyintermittently by contacts 1 40- attached to the vibrating armature 3of the regulator 24, to control the generator voltage.

A resistor 38 may be used in series with voltage,

or shunt, winding 2 of the regulator 24.

In the regulator magnet structure of Fig. 5 5

winding 2, contacts 1, armature 3, spring 4 and air-gaps 5 and 6correspond to like-designated parts of Figs. 1 and 3. Winding I3 ispreferably used in some embodiments of Fig. 5 but in other embodimentsmay not be preferred. Winding I3 50 corresponds to the like-designatedpart in Figs. 1

and 3. Winding 9, magnetic member 8 and airgaps III and II correspond tolike-designated parts of Fig. 1. Winding 20, air-gaps I1 and I8 andmagnetic members I 4, I5 and I6 correspond to like-designated parts ofFig. 3 except that member I6 has additionally a restricted section I2corresponding in proportions and function to restricted section I2 ofFig. 1.

The action of the combination comprised by so' winding 9, member 8,air-gaps I8 and II and restricted section I2' is as described forFig. 1. The action of the combination comprised by winding 28, memberI9, restricted section 2|, airgaps I1 and I8 and member I5 is asdescribed 65 for Fig. 3. Thus the ,regulation provided by the regulatorwill have a volt-ampere regulation as in Fig. 6 characterized by asudden initial droop of voltage at a small increase of current abovezero, thence a substantially uniform voltage regulation over asubstantial range of current increase and finally a relatively suddendroop oi.' voltage beginning at a high current. According to the detailsof the embodiment the regulating characteristic may be of the type shownby dotted line a b c d or of the type shown by solid line a b c d, asexplained more particularly hereinafter.

The regulator is preferably adjusted so that at condition b in Fig. 6the regulated voltage is of a value to cause a suitably low finishingvcurrent to be delivered into the battery after full charge is attained,i. e. the coordinates of point b represent preferred finishing values ofvoltage and current.

The electric circuits of Fig. 5 are as follows: The main, or power,circuit, which is shown in heavy lines, starts from the positive`terminal oi generator 22, passes through a conductor 3| to the positiveside of battery 25, then from the negative terminal of the batterythrough the contacts oi cutout 26, then through series, or currentwinding 28 of the cutout, and then through current, or series, windingsI3, 9 and 2|) of the regulator, in series, and back to the negativeterminal of generator 22. The energizing circuit for the ileld winding23 of generator 22 may be traced as follows: From the positive side ofthe generator, through conductor 3|, conductor 32, regulating resistance29, conductor 33, iield winding 23 and back to the negative side of thegenerator. Contacts 1 are connected, by means o1 conductors 34 and 35,so as to be capable of short circuiting regulating resistance 29. 'Ihemain control, voltage, or shunt, Winding, 2 of the regulator isconnected across the generator 22 as follows: From the positive terminalof the generator 22, through resistance 30, winding 2, conductor 36, andback to the negative side of the generator 22 through the relatively lowresistance current windings I3, 9 and 20 in series. Similarly, thepotential, or shunt, winding 21 of cutout 26 is energized as follows:From the positive side of generator 22, conductor 3|, the winding 21,and back to the negative side of generator 22 through the relatively lowresistance current .windings I3, 9 and 20 'in series.

The vibratory contact regulator action of regulator 2l is believed to bewell understood by those skilled in the art. Briefly stated, it is asfollows: When contacts 1 are closed, resistance 28 is short circuited,consequently the current in field winding 23 increases and the voltageof generator 22 increases. As soon as the voltage of generator 22increases, the current in winding 2 increases, so that the ilux' inair-gaps 5 and 6 increases thereby attracting armature 3 and openingcontacts 1. This causes resistance 29 to be inserted in 'the circuit offield winding 23, thereby reducingk the current in this winding. This inturn reduces the voltage of generator 22 so that contacts 1 again close.This action is repeated very rapidly so that the voltage of generator 22remains at a substantially steady normal value during normal operation.

'I'he operation of Fig. 5 will now be described in a general way,deferring until later the explanation of certain small eiects caused byleakages and saturation.

At very low speeds the generator 22 will generate insuilicient voltageto closethe cutout 26. As the generator speed increases its voltage willincrease until the cutout is closed by its own voltage coll 21. Prior tothe closing of the cutout no current flows in winding 20, consequently.the regulator does not begin to regulate at any voltage less thanvoltage a in Fig. 6. Although the cutout is adjusted so that it does notclose under any condition ata voltage less than the 4battery terminalvoltage, (e in Fig. 6) an ample margin of voltage, up to a in Fig. 6, isprovided wherein to energize the cutout voltage winding suiiiciently toclose the cutout.

A moderate further increase of generator v5 speed after the cutout hasclosed will cause the voltage to rise to a value at which regulationbegins. By virtue of the construction of Fig. 3 as explainedhereinbefore, the iiow of even a small current from the generator tocharge the 10 battery causes the regulated voltage to decline from thcno-load value a to the value b as in Fig. 6. At currents greater than bin Fig. 6 the restricted section 2| is highly saturated, hence thefeature of Fig. 3 exerts substantially 1'5 no further eiect. At currentsless than c in Fig. 6 the restricted section I2 is still unsaturated,hence the principal feature of Fig. l has not yet begun to exert itseffect. The voltage 'between b and c is therefore regulated to a sub- 20stantially constant value. If the charging current is greater than c,restricted section I2' becomes saturated, hence, as explained inconnection with Fig. 1, the voltage regulation droops from c to d as inFig. 6. A battery whose charge 25 is substantially, but not absolutely,exhausted has a counter-electromotive force which although less thannormal is nevertheless fairly high so that when charging is resumed thedroop c d effectively protects the generator against se- 30 vereoverload. Even when the battery has been absolutely discharged so thatits open-circuit voltage is zero, the droop beyond point d of Fig. 6protects the generator against unlimited load at the instant whencharging is resumed. It is 35 'our observation, moreover, that' when abattery which is absolutely discharged, but not ruined, resumescharging, its counter E. M. F. rises almost immediately to roughlyone-half normal so that the generator load declines almost immediately40 from the instantaneous inrush to a value such as point d or d' ofFig. 6.

In describing the operation of Fig. 3 we showed that a slight degree ofdroop, as b c in Fig. 4 occurs over the entire range of currents beyond45 value b at which restricted section 2| becomes saturated. Indescribing the operation of Fig. 1 we showed that even the slightreluctance of restricted section I2 while still unsaturated tends tocause a slight droop such as b c'in Fig. l. 50 When the constructions ofFigs. 1 and 3 are combined as in Fig. 5, these two droops tend to beadditive. Accordingly, the regulation tends to be very distinctlydrooping in the manner of b c of Fig. 6. However, we have also shown 55that in the preferred arrangement of Fig..1 magnetic leakage from theright hand end of member 8 into the bottom, sides and rear of armature 3compensates for droop tending to be caused by the initial reluctance ofrestricted sec- 00- tion I2. By proper proportions and adiustment of thestructure so that the leakage from 8 to the bottom, sides and rear ofarmature 3 is of suihcient magnitude both theseeftects can becompensated s'o that the voltage is substantially 55 Iiat from b to c inFig. 6. It may be preferred, however, to provide the compensation by theinclusion of differential series winding I3 connected and eiiective inthe manner described under Figs. k1 and 3, thereby providing regula- 70tion at substantially uniform voltage between b' and c.

In a practical battery-charging installation, particularly in a 6`voltsystem on an automobile, the resistance of the cutout contact plus 75regulator terminals a closely constant voltage from b to c, the chargingvoltage actually at the battery terminals may droop very substantiallyat the higher charging currents within the'range b c. As will beunderstood by persons well i versed in the battery charging. art, aresult of such a condition is that as the battery is brought up towardfull charge, a substantial decline of charging current occurs earlierthan necessary or advantageous, hence the maximum effectiveness of thesystem within the capacity of the generator is not obtained.. To improvethe effectiveness of charging under this condition it is practicableactually to over-compensate the regulator action by the use ofsufllcient differential series turns in winding I3 eiective upon themain magnet core. A characteristic has been obtained thereby in whichthe voltage at the regulator terminals rises appreciably from point b topoint c so as to compensate for nearly all of the resistance `voltagedrop between the regulator and the battery.

The regulator of Fig. 5 may be provided with adjustments for differentconditions of service or to correct for slight variations inmanufacture. To raise the entire level of the voltage in Fig. 6, i. e.to raise points a, b, c and d by approximately equal amounts the mainair-gaps 5 and 6, or one of them as 6, may be lengthened therebyrequiring a greater current in winding ltov excite the necessary ux forvibratory operation of armature 3. To increase the current at whichpoint c occurs (i. e. the current at which the droop begins for thepurpose of limiting the maximum generator current) air-gaps I0 and IIare lengthened, thereby requiring increased currents in winding 9 forthe attainment of equal degrees of saturation of restricted section I2':The sudden droop in voltage from a to b may be increased most readily byincreasing the reluctance of air-gaps I l and I8, for example bypositioning member I5 farther to one side in a manner which reduces thearea of air-gaps II and I8. This does two things: it increases therequired current in winding 2l for saturating restricted section 2I,hence it moves point b to the right in Fig. 4 or Fig. 6 and it providesthat a greater fraction of the flux excited-by winding 20 traverses mainair-gaps 5 and 6, hence it in-4 creases the spread vertically betweenpoint a and point b. v

If it is desired to increase the droop from a to b but without anincrease in the current at b, the reluctance of air-gaps I1 and Il maybe increased and turns added to winding 2l.

The mechanical details for making and ixing the various air-gapadjustments described are t' not indicated in the drawing but can bereadily supplied, as desired, as will be well understood the length ofthe main magnetic circuit may be comprised of ferro-magnetic material.

Furthermore, the invention is not limited to those arrangements in whichwindings 9 and 2li',

or their equivalents, have, within their respec- :5

tive zones of influence, actions additive, to that of winding 2, or itsequivalent. We conceive that for other uses winding 9, or itsequivalent,'wind ing 20, or its equivalent, either or both, may beconnected for a polarity opposite to that described 10 hereinbefore sothat when thus connected either or both may act subtractively to theaction of winding 2 or its equivalent.

While we have described what we at present consider the preferredembodiments of our invenl5 tion, it will be obvious to those skilled inthe art that various changes and modifications may be made withoutdeparting from our invention and we, therefore aim in the appendedclaims to cover all such changes and modifications as fall 20 within thetrue spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:

1. An electromagnet having, in combination,

a main magnetic circuit, means for producing a 25 unidirectional mainflux in said circuit, an auxiliary magnetic circuit which includes aportion of said main magnetic circuit, said portion being magneticallysaturable, and means for producing a flux in said auxiliary circuitsuillcient to sata- 30 rate magnetically said portion.

2. A magnet structure including a core mem ber, means for producing aunidirectional flux in said core member, a portion of said core memberhaving a restricted cross section whereby said 35 portion ismagnetically saturable at lower values of flux than the rest of saidcore, a magnetic by-pass member around the portion of said core havingsaid restricted cross section whereby a magnetic circuit including saidportion and said by-pass is formed. and an exciting winding for saidcircuit for producing a flux in said portion which is in the oppositedirection from the flux in said core member.

3. 'I'he combination with a main magnetic cir- 5 cuit including a maincore of magnetic material, an air gap, andan armature of magneticmaterial, of an auxiliary magnetic circuit which includes a portion ofsaid-main core, said portion having a restriction therein, anda windingfor-said auxiliary circuit for magnetizing it sufficiently to saturatemagnetically said restricted portion.

4. An operating magnet for a generator voltage regulator comprising amain core', a voltage winding on said core, a portion of said corehaving a.V reduced cross section, magnetic means forming a magneticshunt about said portion, and a current winding for circulating ilux inthe magnetic circuit formed by said portion and said shunt.

5. An electrical regulator having in combina- 6. In combination, amagnetic circuit, a plurality of direct current magnetizing windings forproducing a resultant unidirectional operating flux in said circuit, andmeans magnetized by one of said windings for. preventing said windingfrom pron ducing any substantial change in said operating flux within agiven range of energization of said winding and i'or causing saidwinding to produce a substantial change in said operating ilux overanother range oi energization of said winding.

7. In combination, a magnetic circuit `including a core of magneticmaterial having a pole face, a bar type armature adapted to be attractedto said pole face by nux in said circuit, a plurality of magnetizingwindings for producing flux in said core, and means magnetized by one ofsaid windings and utilizing the phenomenon oi magnetic saturation for.preventing said winding from producing any substantial change in ilux insaid circuit over a given range of energization oi' said winding and forcausing said winding to produce a substantial change in flux in saidcircuit over a diierent range of energization of said winding.

8. An electromagnet having, in combination, a

' main magnetic circuit, means for producing a unidirectional main iluxin said circuit, an auxiliary magnetic circuit which includes a portionofsaid main circuit, said portion being magnetically saturable, andmeans for producing a variable unidirectional ilux in said auxiliarycircuit in such a direction that said variable flux is opposite indirection to said main flux in said portion, said auxiliary flux havingcertain values sumcient to saturate magnetically said portion. 9. Amagnet structure including an exciting winding, a magnetic coreextending through and beyond said winding, the extension beyond saidwinding having a restricted cross-section through at least part of itslength characterized by substantially no reluctance at low and moderateflux densities and substantially great reluctances at high iluxdensities, a magnetic by-pass member characterized by a substantiallyconstant reluctance magnetically in parallel with said restricted-cross-section and an exciting winding on said by-pass member forcirculating flux in said variable reluctance restricted section.

10. The combination with a main magnetic circuit having a main core, anair gap, an armature,

- and a direct current exciting winding for producing a unidirectionalmain ilux in said circuit, of an auxiliary magnetic circuit having anauxiliary core, an air gap, a portion of said main core,and a directcurrent exciting winding on said auxiliary core for producing a'unidirectional ux in said auxiliary magnetic circuit which is oppositeto the main ilux in said portion of said main core, said portion beingmore readly magnetically saturablethan the rest of said main core.

11. An operating magnet for a generator voltage regulator comprising amain core, a voltage winding for producing a unidirectional flux in saidcore, a portion of said core having a restricted cross section, amagnetic shunt around said restricted portion whereby a magnetic circuitin- ,cluding said portion and said shunt is formed, and a currentwinding on said shunt`for producing a unidirectional ilux in4 saidcircuit which is opposite in direction in said portion to the fluxproduced by said voltage winding.

l2. In combination, a magnetic circuit including a core of magneticmaterial having a pole face, a bar type armature adapted to be attractedto said pole face by ilux in said circuit, a plurality f of magnetizingwindings for producing flux in said core, andmeans utilizing thephenomenon of magnetic saturation and magnetized by one of said windingsfor preventing said winding from producing any substantial change influx in said circuit over a given range of energization o! said tion ofsaid winding whose values are less than the winding and for causing said.windings to'produce a substantial change in ilux in said circuit over adifferent, range of energization of said winding whose values aregreater than the values of said rst mentioned range. 5

13. An electromagnet having, in combination, a mainmagnetic circuit,means for producing a unidirectional main flux in said circuit, anauxiliary magnetic circuit which includes a portion of said maincircuit, said portion being magnetically saturable, and means forproducing a variable unidirectional flux in said auxiliary circuit insuch a direction that said variable iiux is in the same direction assaid main ilux in said portion, said auxiliary ilux having certainvalues suiicient to saturate magnetically said portion.

14. A magnet structure including an exciting winding, a. magnetic coreextending through and beyond said winding, the extension beyond saidwinding'having a restricted cross-section through 20 at leastl part ofits length characterized by substantially no reluctance at low andmoderate flux densities and substantially great reluctances at highfiuxdensities, a magnetic by-pass member of substantially constantreluctance, said by-pass being arranged magnetically in parallel to saidi restricted section,'and an exciting winding about that portion of saidextension which is paralleled byy said by-pass member.

15. The combination with a main magnetic circuit having a main core, anair gap, an armature, 'and a direct current exciting winding forproducing a unidirectional main ilux in said circuit of an auxiliarymagnetic circuit having an auxiliary core, an air gap and a portion ofsaid main core, a direct current winding on said portion oi.' said maincore for producing -a unidirectional auxiliary flux in the samedirection in said portion as said main ilux, said portion beingconstructed to saturate magnetically at lower values of iiux than therest of said main core.

16. An operating magnet for a generator voltage regulator comprising amain core, a voltage winding for producing a unidirectional flux in saidcore, a restricted section in said core, a magnetic shunt around saidrestricted section whereby a magnetic circuit including said shunt andsaid restricted section is formed, and a. current Winding on saidrestricted section for producing a unidirectional ilux therein which isin the same direction therein as the flux produced by said voltagewinding.

17. In combination, a magnetic circuit including a coreof magneticmaterial having a pole face, a bar type armature adapted to be attractedto said pole face by ilux in said circuit, a plurality of magnetizingwindings for producing ilux in said core, and means utilizing thephenomenon of magnetic saturation for preventing one of said windingsfrom producing any substantial change in flux in said circuit over agiven range of energization of said winding and for causing said windingto produce a substantial change in ilux in said circuit over adiil'erent range of energizavalues o! said first mentioned range.

18. A generator voltage regulator having in combination an operatingmagnet, a plurality of current coils associated with said magnet, one ofsaid current coils being arranged to saturate magnetically a portion ofsaid magnet at currents above a predetermined low value, and another ofsaid current coils being arranged to saturate magnetically a portion ofsaid magnet at currents above a predetermined high value.

19. In combination, a U-shaped core of magnetic material, an amature forcompleting a magnetic circuit through said core, means for producing amain flux in said circuit, air gaps between 'said armature and saidcore, an eiective pivot for said armature so positioned that the turningmoment on said armature produced by the ux at one air gap is greaterthan the turning moment produced at the other air gap, a restriction insaid core adjacent the air gap which produces the greater turningmoment, flux producing means for circulating flux through saidrestriction, said iiux producing means producing a leakage fiux whichenters said armature and returns in two components through said airgaps, respectively, the relative directions of said main flux and thecomponents of said leakage uir in said air gaps being such that theeffect of said leakage fiux is to weaken the moment at the air gap atwhich the moment is the stronger and to strengthen the moment at the airgap at which the moment is the weaker.

BENJAMIN R. TEARE, Jn. MAX A. WHITING.

Y (Seal) ('IERTIFICATJV 0F CORRECTION.

Patent No. 2,014,869.'

BENJAMIN R. TEARE, Jn., Er AL.

lt is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as'follows: Page 8,second column, l line l, claim 12, for "windings" read winding; and thatthe said Letters Patent should be read with this correction therein thatthe same may conform to the record of the case in the Patent Office.

I signed and sealed :his smday ,of November, A; D. 1935.

Leslie Frazer Acting Commissioner of Patents.

September .17, 1935.

tnmrlrlcATEY 0F CORRECTION. Patent No. 2, 014,869.-

September 17, 1935.

BENJAMIN R. TEARE, JR., ETYAL.

1t is hereby certified that error appears in theprinted specification ofthe above numbered patent requiring correction asvfollows: Page 8,second column,

line 1, claim 12, for "windings" read winding; and that the said LettersPatent should be read wi th this correction therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this Sth-day of November, A.. D. 1935.

Leslie Frazer (Seal) Acting Commissioner of Patents.

